In recent years, photopolymerization, including cationic photopolymerization, has been the object of intense research because of the continued growth of academic and industrial applications for new monomers and/or photoinitiator systems. The use of photoinitiators increases steadily not only for traditional applications such as coatings, inks and adhesives but also more recently in high-tech applications such as optoelectronics, stereolithography and nanotechnology.
Photopolymerization offers many advantages compared to conventional thermal polymerization, such as the spatial control of the initiation, and the fact that polymerization can be carried out without solvent and therefore to reduced cost. Another important advantage is that it can be performed at room temperature, unlike thermal polymerization which often requires a high temperature, thereby allowing gains in terms of economic and energy cost savings. Finally, cationic polymerization is generally not oxygen-sensitive, which is a major advantage because it does not require the use of an inert atmosphere. Thus, cationic photopolymerization combines all the aforementioned advantages.
Thus far, most of the formulations used in photopolymerization have been usable only with high intensity UV lamps. This results in safety problems for the operator due to the wavelength used, in addition to a non-optimal energetic efficiency, thereby reducing the scope of this approach. To overcome these problems, the use of mild irradiation conditions is therefore a major challenge and the development of new highly absorbent in the visible and allowing the use of light emitting in the visible and low consumption initiators are actively sought both at industrial level and academic.
Therefore, there remains a need for the development of new initiator systems that trigger photopolymerization under mild conditions, for example using visible light.